Connected epitaxial optical sensing system comprising a trench deeper than a waveguide of a light source electrically isolates the light source and a detector

ABSTRACT

A device including a plurality of epitaxial chips is disclosed. An epitaxial chip can have one or more of a light source and a detector, where the detector can be configured to measure the optical properties of the light emitted by a light source. In some examples, one or more epitaxial chips can have one or more optical properties that differ from other epitaxial chips. The epitaxial chips can be dependently operable. For example, the detector located on one epitaxial chip can be configured for measuring the optical properties of light emitted by a light source located on another epitaxial chip by way of one or more optical signals. The collection of epitaxial chips can also allow detection of a plurality of laser outputs, where two or more epitaxial chips can have different material and/or optical properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.16/651,901, filed Mar. 27, 2020, now U.S. Pat. No. 11,156,497, which isa national phase application under 35 U.S.C. § 371 of PCT/US2018/052669,filed Sep. 25, 2018, which claims the benefit of U.S. Provisional PatentApplication No. 62/566,027, filed Sep. 29, 2017, which are herebyincorporated by reference in their entirety.

FIELD

This relates generally to a plurality of dependently operable epitaxialchips included in a device. More particularly, this relates to epitaxialchips each including a detector configured for measuring the opticalproperties of light emitted by a light source located on anotherepitaxial chip.

BACKGROUND

Optical sensing systems can be useful for many applications, such astrace gas detection, environmental monitoring, biomedical diagnostics,telecommunications, and industrial process controls. In some instances,it may be useful to measure the optical properties of light emitted bythe light sources. For example, the optical properties of emitted lightcan be monitored to ensure that the light source is tuned to thetargeted wavelength and/or targeted power density.

One way to be able to monitor the optical properties of light emitted bya light source can be to include a detector in the optical sensingsystem that directly measures the emitted light. The light source can begrown and processed separately on a different epitaxial chip than thedetector, where optical traces can be used to route signals between thelight source and the detector. Some optical sensing system can includean integrated photonics optical sensing system, which can include aplurality of light sources and detectors. One way to reduce thecomplexity and the number of epitaxial chips included in the opticalsensing system can be to integrate the light source and the detector onthe same epitaxial chip. Epitaxial chips can be configured to operateindependently, where on the same epitaxial chip, the detector canmeasure the optical properties of the emitted light from the lightsource. In some instances, independent operation can lead to leakagecurrent flowing from the light source through one or more conductivelayers to the detector, where the leakage current can mask the detectorcurrent.

SUMMARY

A device including a plurality of epitaxial chips is disclosed. Anepitaxial chip can have one or more of a light source and a detector,where the detector can be configured to measure the optical propertiesof the light emitted by a light source. In some examples, one or moreepitaxial chips can have one or more optical properties (e.g., bandstructure) that differ from other epitaxial chips. For example, acollection of epitaxial chips can allow the optical sensing system toemit a broader range of wavelengths (e.g., red, green, and blue colors)than a single epitaxial chip. The epitaxial chips can be dependentlyoperable. For example, the detector located on one epitaxial chip can beconfigured for measuring the optical properties of light emitted by alight source located on another epitaxial chip by way of one or moreoptical signals. The collection of epitaxial chips can also allowdetection of a plurality of laser outputs, where two or more epitaxialchips can have different material and/or optical properties. Lightsources located on one or more first epitaxial chips can be driven,while the detectors located on one or more second epitaxial chips can beconfigured for optical sensing during a first time period. During asecond time period, the light sources located on the second epitaxialchip(s) can be driven, while the detectors located on the firstepitaxial chip(s) can be configured for optical sensing. In someinstances, the light source and the detector included in the sameepitaxial chip can be electrically isolated by creating a trench thatcan be deeper than one or more (e.g., all) conductive layers included inthe epitaxial wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a portion of an exemplarydevice according to examples of the disclosure.

FIG. 2A illustrates a block diagram of an exemplary device includinglight sources and detectors located on separate epitaxial chipsaccording to examples of the disclosure.

FIG. 2B illustrates a block diagram of an exemplary portion of anepitaxial chip according to examples of the disclosure.

FIG. 2C illustrates a cross-sectional view of a plurality ofindependently operable epitaxial chips according to examples of thedisclosure.

FIG. 3A illustrates a top-view of a plurality of dependently operableepitaxial chips according to examples of the disclosure.

FIG. 3B illustrates a cross-sectional view of a plurality of dependentlyoperable epitaxial chips according to examples of the disclosure.

FIG. 4A illustrates a change in the band structure of an exemplary lightsensor with temperature according to examples of the disclosure.

FIG. 4B illustrates the band structures of an exemplary light sensor andan exemplary detector located on different epitaxial wafers according toexamples of the disclosure.

FIG. 4C illustrates a gain curve from an exemplary light source and aresponsivity curve from an exemplary detector, where the epitaxial chipscan be independently operated according to examples of the disclosure.

FIG. 4D illustrates a gain curve from an exemplary light source and aresponsivity curve from an exemplary detector located on dependentlyoperable epitaxial chips according to examples of the disclosure.

FIG. 5 illustrates an exemplary flow for operating a device including aplurality of dependently operable epitaxial chips according to examplesof the disclosure.

FIG. 6 illustrates a block diagram of an exemplary device including aplurality of epitaxial chips according to examples of the disclosure.

FIG. 7 illustrates a cross-sectional view of an exemplary epitaxialwafer including a trench for electrical isolation according to examplesof the disclosure.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings in which it is shown by way of illustrationspecific examples that can be practiced. It is to be understood thatother examples can be used and structural changes can be made withoutdeparting from the scope of the various examples.

Various techniques and process flow steps will be described in detailwith reference to examples as illustrated in the accompanying drawings.In the following description, numerous specific details are set forth inorder to provide a thorough understanding of one or more aspects and/orfeatures described or referenced herein. It will be apparent, however,to one skilled in the art, that one or more aspects and/or featuresdescribed or referenced herein may be practiced without some or all ofthese specific details. In other instances, well-known process stepsand/or structures have not been described in detail in order to notobscure some of the aspects and/or features described or referencedherein.

Further, although process steps or method steps can be described in asequential order, such processes and methods can be configured to workin any suitable order. In other words, any sequence or order of stepsthat can be described in the disclosure does not, in and of itself,indicate a requirement that the steps be performed in that order.Further, some steps may be performed simultaneously despite beingdescribed or implied as occurring non-simultaneously (e.g., because onestep is described after the other step). Moreover, the illustration of aprocess by its description in a drawing does not imply that theillustrated process is exclusive of other variations and modificationthereto, does not imply that the illustrated process or any of its stepsare necessary to one or more of the examples, and does not imply thatthe illustrated process is preferred.

A device including a plurality of epitaxial chips is disclosed. Anepitaxial chip can have one or more of a light source and a detector,where the detector can be configured to measure the optical propertiesof the light emitted by a light source. In some examples, one or moreepitaxial chips can have one or more optical properties (e.g., bandstructure) that differ from other epitaxial chips. For example, acollection of epitaxial chips can allow the device to emit a broaderrange of wavelengths (e.g., red, green, and blue colors) than a singleepitaxial chip. The epitaxial chips can be dependently operable. Forexample, the detector located on one epitaxial chip can be configuredfor measuring the optical properties of light emitted by a light sourcelocated on another epitaxial chip by way of one or more optical signals.The collection of epitaxial chips can also allow detection of aplurality of laser outputs, where two or more epitaxial chips can havedifferent material and/or optical properties. Light sources located on aone or more first epitaxial chips can be driven, while the detectorslocated on one or more second epitaxial chips can be configured foroptical sensing during a first time period. During a second time period,the light sources located on the second epitaxial chip(s) can be driven,while the detectors located on the first epitaxial chip(s) can beconfigured for optical sensing. In some instances, the light source andthe detector included in the same epitaxial chip can be electricallyisolated by creating a trench that can be deeper than one or more (e.g.,all) conductive layers included in the epitaxial wafer.

Representative applications of methods and apparatus according to thepresent disclosure are described in this section. These examples arebeing provided solely to add context and aid in the understanding of thedescribed examples. It will thus be apparent to one skilled in the artthat the described examples may be practiced without some or all of thespecific details. Other applications are possible, such that thefollowing examples should not be taken as limiting.

Optical sensing systems can have many uses in portable (e.g.,compact-sized) electronic devices. FIG. 1 illustrates a cross-sectionalview of an exemplary portion of a device according to examples of thedisclosure. The device 100 can include a plurality of light sources 102,a detector 130, and an optics unit 129. The term “device” as usedthroughout can refer to a single standalone component that can operatealone for a given function, or can refer to a system including multiplecomponents that operate together to achieve the same functions. Thedevice 100 can include optical components such as a plurality of lightsources 102, a detector 130, and an optics unit 129. As used throughoutthis specification, a system, such as an optical sensing system, caninclude a device.

The light sources 102 can be configured to emit light 141. The lightsources 102 can be any type of source capable of generating lightincluding, but not limited to, a laser, a light emitting diode (LED), anorganic light emitting diode (OLED), an electroluminescent (EL) source,a quantum dot (QD) light source, a super-luminescent diode, asuper-continuum source, a fiber-based source, or a combination of one ormore of these sources. In some examples, one or more light sources 102can be capable of emitting a plurality of wavelengths (e.g., a range ofwavelengths) of light. In some examples, one or more of the lightsources 102 can emit a different wavelength range of light (e.g.,different colors in the spectrum) than the other light sources 102.

Light from the light sources 102 can be combined using one or moreintegrated tuning elements 104, optical traces (not shown), one or moremultiplexers (not shown), and/or other optical components. In someexamples, the integrated tuning elements 104, the optical traces, andthe multiplexer(s) can be disposed on a substrate 142. The substrate 142can be included in a single optical platform, such as an integratedsilicon photonics chip. An integrated silicon photonics chip can also beknown as a photonics integrated chip (PIC). The device 100 can alsoinclude a thermal management unit 101 for controlling (e.g., heating orcooling, including stabilization) the temperature of the light sources102. One or more outcouplers 109 can be coupled to the integrated tuningelements 104, optical traces, and/or multiplexers. The outcouplers 109can be configured to focus, collect, collimate, and/or condition (e.g.,shape) an incident light beam to form light 150, which can be directedtowards the system interface (e.g., the external housing of the device100).

Light can be light emitted from the light sources 102, collimated by theoutcouplers 109, and transmitted through the optics unit 129. At least aportion of light 150 can return to the device 100. The return light canbe transmitted through the optics unit 129 and can be incident on thedetector 130. In some examples, the return light may transmit throughdifferent optics included in the optics unit 129 than light 150.

In some instances, it may be useful to measure the optical properties oflight emitted by the light sources. For example, the optical propertiesof light 148 can be measured to ensure that the light source is tuned toa targeted wavelength(s). One way to be able to monitor the opticalproperties of emitted light can be to include a detector that directlymeasures the emitted light 148. Some device s can include a plurality oflight sources and detectors, which can lead to a large number ofepitaxial chips if a large number of wavelengths is desired and thelight sources and the detectors are located on separate epitaxial chips.

One way to reduce the number of epitaxial chips and the complexity canbe to integrate a light source and a detector on the same epitaxialchip. FIG. 2A illustrates a block diagram of an exemplary deviceincluding light sources and detectors located on separate epitaxialchips according to examples of the disclosure. The device 200 caninclude a plurality of epitaxial chips 201. Each epitaxial chip 201 canbe configured to emit light 248 towards the outcoupler 209. Light 248can be directed along multiple path ways using waveguides 205, forexample. The outcoupler 209 can redirect light 248 out of the device200, as discussed earlier. In some examples, one or more epitaxial chips201 can have one or more optical properties (e.g., band structure) thatdiffer from other epitaxial chips 201. For example, the epitaxial chip201A can be configured to emit light having a first range of wavelengths(e.g., red colors), the epitaxial chip 201B can be configured to emitlight having a second range of wavelengths (e.g., green colors), and theepitaxial chip 201C can be configured to emit light having a third rangeof wavelengths (e.g., blue colors). The collection of epitaxial chips201 can allow the device 200 to emit a broader range of wavelengths(e.g., red, green, and blue colors) than a single epitaxial chip 201.

FIG. 2B illustrates a block diagram of an exemplary epitaxial chipaccording to examples of the disclosure. The epitaxial chip 201 caninclude a light source 202, one or more waveguides 205 (optional), and adetector 232. In some examples, the epitaxial chip 201 can include aplurality of discrete detectors associated with individual waveguides.The output from one or more of the waveguides 205 can be routed (e.g.,via optical traces) to the detector 232 such that the detector 232 canmeasure the optical properties (e.g., monitor the power density) oflight emitted by the light source 202. The detector 232 and the opticaltraces (e.g., associated with optical signal 204) can be located on thesame epitaxial chip, and the epitaxial chips 201 can operateindependently (discussed below) such that light can be generated and theproperties of the generated can be measured without the need foradditional epitaxial chips, for example. Based on the measured opticalproperties, the detector 232 can communicate with a controller (notshown), for example, to adjust one or more waveforms to drive the lightsource 202.

FIG. 2C illustrates a cross-sectional view of a plurality ofindependently operable epitaxial chips according to examples of thedisclosure. Epitaxial chip 201A can include a light source 202A and adetector 232A. Epitaxial chip 201B can include a light source 202B and adetector 232B. Within a given epitaxial chip, the detector (e.g.,detector 232A) can be configured for measuring the optical properties oflight emitted by the light source (e.g., light source 202A) by way of anoptical signal (e.g., optical signal 204A). During operation, the lightsource and the detector included in the same epitaxial chip can bedriven simultaneously. That is, the epitaxial chips can operateindependently (e.g., optical signals 204 may not be shared betweenepitaxial chips). One effect of driving the light source and thedetector simultaneously can be leakage current 211. The leakage current211 can flow from the light source through a conduction portion (e.g.,conductive layers 234) to the detector in the same epitaxial chip. Insome instances, the amount of leakage current 211 can be higher than thedetector current, which can cause the leakage current to mask thedetector current. Masking the detector current can reduce the detector'slikelihood of accurately determining the optical properties of theemitted light.

One way to reduce (or eliminate) the leakage current can be to configurethe epitaxial chips to operate dependently. FIG. 3A illustrates a blockdiagram of an exemplary device including light sources according toexamples of the disclosure. The device 300 can include a plurality ofepitaxial chips 301. Each epitaxial chip 301 can include a plurality ofwaveguides 305 and can be configured to emit light 348 towards theoutcoupler 309. The outcoupler 309 can redirect light 348 out of thedevice 300, as discussed earlier. In some examples, one or moreepitaxial chips 301 can have one or more optical properties (e.g., bandstructure) that differ from other epitaxial chips 301. For example, theepitaxial chip 301A can be configured to emit light having a first rangeof wavelengths (e.g., red colors), the epitaxial chip 301B can beconfigured to emit light having a second range of wavelengths (e.g.,green colors), and the epitaxial chip 301C can be configured to emitlight having a third range of wavelengths (e.g., blue colors).

Each epitaxial chip 301 can include a light source 302 and a detector332. For example, the epitaxial chip 301A can include a light source302A and a detector 332A. The epitaxial chip 301B can include at leastone light source 302B and at least one detector 332B, and the epitaxialchip 301C can include a light source 302C and a detector 332C. Theepitaxial chip 301A can be located adjacent (i.e., no other epitaxialchips located in between) to the epitaxial chip 301B, which can belocated adjacent to the epitaxial chip 301C.

In some examples, the light source 302 and the detector 332 included onthe same epitaxial chip 301 can be grown and engineered from the sameepitaxial wafer. That is, the materials included in the light source 302and the detector 332 included in the same epitaxial chip 301 can be thesame. By using different biasing schemes, the same materials can beconfigured to operate differently. That is, the light source 302 can beconfigured to operate as a light emitter, and the detector 332 can beconfigured as a light sensor. For example, a positive bias (e.g., +2V)can be applied to the light source 302, while a negative bias (e.g.,−2V) can be applied to the detector 332.

The detector (e.g., detector 332B) located on one epitaxial chip (e.g.,epitaxial chip 301B) can be configured for measuring the opticalproperties of light emitted by a light source (e.g., light source 302A)located on another epitaxial chip (e.g., epitaxial chip 301A) by way ofthe optical signal (e.g., optical signal 304A) associated with therespective linked light source-light detector set. In some examples,within a linked light source-light detector set, the detector can beincluded in an epitaxial chip proximate (e.g., adjacent) to theepitaxial chip that the light source is included in. Examples of thedisclosure can include any number of light sources and light detectorsincluded in a linked light source-light detector set.

As an example, the detector 332B can measure the optical properties ofthe optical signal 304A from the light source 302A. As another example,the detector 332C can measure the optical properties of the opticalsignal 304B from the light source 302B. In this manner, the epitaxialchips 301 can operate dependently. The outcoupler 309 may receive thesame light 348 and may not be affected by dependent operation of theepitaxial chips 301. By electrically separating the light source and thedetector onto different epitaxial chips 301, the leakage current (e.g.,leakage current 211 illustrated in FIG. 2C) between the two opticalcomponents can be prevented or reduced.

Although the figure illustrates three epitaxial chips, examples of thedisclosure can include any number of epitaxial chips. Additionally,although the figure illustrates each epitaxial chip as including onelight source, three waveguides, and one detector, examples of thedisclosure are not limited to these specific numbers of opticalcomponents on a given epitaxial chip 201. Additionally, examples of thedisclosure are not limited to these types of optical components.

FIG. 3B illustrates a cross-sectional view of a plurality of dependentlyoperable epitaxial chips according to examples of the disclosure. Asdiscussed above, the detector (e.g., detector 332B) on a third epitaxialchip (e.g., epitaxial chip 301B) can be configured to measure theoptical properties of light emitted by the light source (e.g., lightsource 302A) on a first epitaxial chip (e.g., 301A). During operation,the light source (e.g., light source 302B) on the third epitaxial chip(e.g., epitaxial chip 301B) may be activated (e.g., emitting light) atthe same time as the detector (e.g., detector 332B) located on the sameepitaxial chip. In some instances, a leakage current may exist betweenthe light source and the detector on the same epitaxial chip even if theleakage current may be associated with a different optical signal thanthe detector is associated with. For example, simultaneous operation ofthe epitaxial chip 301A and the epitaxial chip 301B can cause leakagecurrent to flow from the light source 302B to the detector 332B on theepitaxial chip 301B. The detector 332B may produce an electrical signal,which may include an indication of one or more properties of the opticalsignal 304A. The electrical signal may also incorrectly include theleakage current (e.g., from light source 302B) from the light source302B. To prevent or reduce the leakage current, the epitaxial chips canbe operated in a certain manner (discussed in detail below).

Although the figure illustrates one detector measuring the opticalproperties of one light source, examples of the disclosure can includeany number of detectors optically coupled to any number of lightsources. For example, one detector can measure the optical properties ofmultiple light sources via optical signals routed using optical traces.The optical signals from the multiple light sources can be combined ormay be transmitted in a time-multiplexed manner to the detector. Asanother example, the optical properties of one light source can bemeasured by multiple detectors. Additionally or alternatively, examplesof the disclosure are not limited epitaxial chips including differenttypes of optical components. For example, at least one epitaxial chipcan include only light source(s) and at least one epitaxial chip caninclude only detector(s).

In addition to reducing the leakage current, dependently operableepitaxial chips can exploit the operating temperature differencesbetween the two different optical components. FIG. 4A illustrates achange in the band structure of an exemplary light sensor withtemperature according to examples of the disclosure. At a firsttemperature (e.g., the temperature before the laser begins lasing), thelight source can have a band structure 424 that includes bandgap energy416. The emission wavelength of the emitted light can correspond to itsbandgap energy, so a change in the bandgap energy can change theemission wavelength. At a second temperature (e.g., the temperatureafter the laser begins lasing, which can be a higher temperature), thelight source can have a band structure 425 that includes a bandgapenergy 417. In some examples, the first temperature can be thetemperature of the light source while the light source is inactive(e.g., no drive waveform is applied), and the second temperature can bethe temperature of the light source while the light source is active(e.g., a non-zero drive waveform is applied). That is, an increase intemperature of the light source can reduce its bandgap energy and canshift the emission wavelength to a longer wavelength.

In some instances, the detector may not be as sensitive to temperaturechanges as the light source. If the light source and the detector areincluded in the same epitaxial wafer, the materials for both opticalcomponents can be the same, as discussed above. When the materials forboth optical components are the same, the bandgap energies of bothoptical components can be the same. If the bandgap of the light sourcechanges due to, e.g., carrier injection, while the bandgap of thecorresponding detector does not change, then the difference in bandgapsmay prevent the detector from absorbing (i.e., detecting) at least someof the light (e.g., lower energy and longer emission wavelengths)emitted by the light source.

If the light source and the detector are included in different epitaxialwafers (e.g., epitaxial wafers grown with different materials havingdifferent bandgaps), then differences in bandgaps can be reduced. FIG.4B illustrates the band structures of an exemplary light sensor and anexemplary detector located on different epitaxial wafers according toexamples of the disclosure. For example, the light source can beincluded in an epitaxial chip having a longer bandgap (e.g., due to adifference in the material growth) than the epitaxial chip that thedetector may be included in. As discussed above, the light source canhave a band structure 424 that includes bandgap energy 416 at a firsttemperature. The light source can undergo an optical shift to the bandstructure 425 and bandgap energy 417 at a second (e.g., higher than thefirst) temperature. The detector can have a band structure 427 thatincludes bandgap energy 419 at both first and second temperatures. Insome examples, the bandgap energy 417 and the bandgap energy 419 can bethe same. When active, the difference in bandgaps can be little to noneand can allow the detector to absorb most or all of the emitted light.

Dependently operating the epitaxial chips can also increase theefficiency of the device. FIG. 4C illustrates a gain curve from anexemplary light source and a responsivity curve from an exemplarydetector, where the epitaxial chips can be independently operatedaccording to examples of the disclosure. The light source can have again curve 440, and the detector can have a responsivity curve 446. Asillustrated in the figure, the wavelength where the maximum gain 441 ofthe light source occurs can differ from the wavelength where the maximumresponsivity 443 of the detector occurs, and this is referred to as thedifference 445. Dependently operating the epitaxial chips can shift theresponsivity curve 446 of the detector relative to the gain curve 440 ofthe light source, as illustrated in FIG. 4D. The shift in theresponsivity curve 446 can allow the maximum gain 441 of the lightsource to be located closer (e.g., within 5%) to the maximumresponsivity 447 of the detector, which can increase the efficiency ofthe device.

FIG. 5 illustrates an exemplary flow for operating the device includinga plurality of dependently operable epitaxial chips according toexamples of the disclosure. Light source(s) located on one or more firstepitaxial chips can be driven, while the detectors located on therespective linked epitaxial chip(s) can be configured for opticalsensing during a first time period. In this manner, the linked epitaxialchips may not be configured with the same mode of operation at the sametime. For example, linked epitaxial chips can include a pair ofepitaxial chips, where one epitaxial chip can be emitting light and theother epitaxial chip can be detecting light. In some examples, theoptical components within a linked light source-light detector set mayoperate in a time-multiplexed manner.

In some examples, a first epitaxial chip can be surrounded by a secondepitaxial chip, and a second epitaxial chip can be surrounded by a firstepitaxial chip. During a second time period, the light sources locatedon the second epitaxial chip(s) can be driven, while the detectorslocated on the first epitaxial chip(s) can be configured for opticalsensing. For example, every even epitaxial chip can be configured forlight emission, and every odd epitaxial chip can be configured fordetecting the optical properties of the emitted light. Each opticalcomponent of a linked (e.g., sharing an optical signal) of lightsource-light detector set can be activated simultaneously.

In some examples, the light source can be driven before the detectorbelonging to the same light source-light detector pair begins sensing.For example, the device can include six epitaxial chips. The first lightsource located on the first epitaxial chip, the third light sourcelocated on the third epitaxial chip, and the fifth light source locatedon the fifth epitaxial chip can be driven (step 552, step 554, and step556 of process 550). In some instances, the first light source, thethird light source, etc. can be operated simultaneously. The seconddetector located on the second epitaxial chip, the fourth detectorlocated on the fourth epitaxial chip, and the sixth detector located onthe sixth epitaxial chip can be configured for optical sensing (step562, step 564, and step 566 of process 550). In some instances, thesecond detectors, the fourth detector, etc. can be operatedsimultaneously. The second light source located on the second epitaxialchip, and the fourth light source located on the fourth epitaxial chipcan be driven (step 572 and step 574 of process 550). The third detectorlocated on the third epitaxial chip, and the fifth detector located onthe fifth epitaxial chip can be configured for optical sensing (step 582and step 584 of process 550).

In some examples, the first and/or second epitaxial chips may have oneor more structures and/or functionalities different from the otherepitaxial chips. FIG. 6 illustrates a block diagram of an exemplarydevice including a plurality of epitaxial chips according to examples ofthe disclosure. Device 600 can include a plurality of epitaxial chips601. The plurality of epitaxial chips 601 can include the firstepitaxial chip 601A and the second epitaxial chip 601N, where theremaining epitaxial chips 601B-601M can be located between the firstepitaxial chip 601A and the second epitaxial chip 601N. For example, thefirst epitaxial chip 601A may only have one neighboring chip (e.g., thethird epitaxial chip 601B).

The detector (e.g., detector 632A) of the first epitaxial chip 601A maynot be associated with an optical signal 604. The detector (e.g., thedetector 632A) of the first epitaxial chip may then be inactive (e.g., a“dummy” detector). That is, the “dummy” detector 632A may have astructure located on the first epitaxial chip 601A, but a bias may notbe applied across the dummy detector 632A. In some examples, the firstepitaxial chip 601A may not include a detector (not shown), and instead,may only include a light source (e.g., light source 602A).Alternatively, the detector of the first epitaxial chip 601A may not beconnected (i.e., deactivated) to any circuitry used for operating thedetector, while the other detectors located on other epitaxial chips maybe connected to circuitry. In this manner, some or all of the epitaxialchips can be grown and processed in the same manner, where the operationof some (e.g., first and/or second) epitaxial chips can be differentthan the operation of other epitaxial chips.

Similarly, the second epitaxial chip 601N (e.g., the tenth epitaxialchip in a device having a total of ten epitaxial chips) may only haveone neighboring chip (e.g., fourth epitaxial chip 601M), so the lightsource (e.g., light source 602N) of the second epitaxial chip 601N maynot be associated with an optical signal 604 measured by a detector. Insome instances, the light source of the second epitaxial chip 601N maybe measured by a detector located on the same epitaxial chip 601N. Thedetector (e.g., detector 632N) may be configured to measure the opticalproperties of light emitted from multiple light sources (e.g., lightsource 602M and light source 602N). The optical signals can be combinedand collectively measured by the detector or may be time-multiplexed.

The light source (e.g., light source 602N) of the second epitaxial chip601N may be inactive (e.g., a “dummy” light source). In some examples,the second epitaxial chip 601N may not include a light source, andinstead, may only include a detector 632N. Alternatively, the lightsource of the second epitaxial chip 601N may not be connected (i.e.,deactivated) to circuitry used to operate the light source, while theother light sources of the other epitaxial chips may be connected tocircuitry. In some examples, the second epitaxial chip 601N may includea light source 602N whose optical properties may not be directlymeasured by a detector. In some examples, an epitaxial chip (e.g., thesecond epitaxial chip 601N) can include the same materials as itsneighboring epitaxial chip (e.g., a fourth epitaxial chip 601M), but maybe configured to operate with a different (e.g., smaller) bandgap energyby heating or cooling the epitaxial chip to a different (e.g., higher)temperature.

Although not shown in the figure, examples of the disclosure can includeone or more epitaxial chips that may different in the type of opticalcomponents relative to the other epitaxial chips. For example, the firstepitaxial chip 601A may not include a detector and/or the secondepitaxial chip 601N may not include a light source. Additionally oralternatively, the epitaxial chips can include optical componentsisolated from other optical components on the same epitaxial chipsusing, e.g., one or more trenches (discussed below).

Another way to reduce the amount of leakage current included in thesignal can be to electrically isolate the light source and the detectorincluded in the same epitaxial chip. FIG. 7 illustrates across-sectional view of an exemplary epitaxial wafer including a trenchfor electrical isolation according to examples of the disclosure.Epitaxial chip 701 can include a light source 702 and a detector 732formed from a stack of materials including a conductive layer 734. Atrench 723 can be formed between the light source 702 and the detector732 to electrically isolate the structures. In some examples, the trench723 can be deeper (e.g., relative to the top of the epitaxial chip 701)than the conductive layer 734 such that a path for leakage current maynot form between the light source 702 and the detector 732. In someexamples, with the electrically isolated structures, the device caninclude heaters coupled to the light source, the detector, or both. Theheaters may be separate heaters capable of controlling the temperature(e.g., heating one or more structures) independently from others. Forexample, a first heater can control the temperature of the light source,and a second heater can control the temperature of the detector. Thefirst heater may not affect the temperature of the detector, and thesecond heater may not affect the temperature of the light source.

Although the figure illustrates the epitaxial chip as including onetrench, one light source, and one detector, examples of the disclosurecan include any number of trenches, light sources, and detectors.

A device is disclosed. The device can comprise: a plurality of epitaxialchips including a first epitaxial chip and a second epitaxial chip, thefirst epitaxial chip includes at least one first structure configured asa light source that emits light, and the second epitaxial chip includesat least one second structure configured as a detector that detectslight, wherein the emitted light from adjacent epitaxial chips havedifferent optical properties, wherein the second epitaxial chip isconfigured to detect the light emitted by the at least one firststructure included in another of the plurality of epitaxial chips.Additionally or alternatively, in some examples, the plurality ofepitaxial chips further includes a subset of epitaxial chips, eachsubset including: at least one first structure configured as a lightsource that emits light, and at least one second structure configured asa detector that detects light from at least one first structure inanother epitaxial chip. Additionally or alternatively, in some examples,each of the subset of epitaxial chips includes a first materialassociated with a first bandgap energy, wherein the another epitaxialchip includes a second material associated with a second bandgap energy,wherein the first bandgap energy is different from the second bandgapenergy. Additionally or alternatively, in some examples, the firstbandgap energy is shorter than the second bandgap energy. Additionallyor alternatively, in some examples, the first material changes to thesecond bandgap energy with an increase in temperature. Additionally oralternatively, at least two of the plurality of epitaxial chips includesdifferent materials associated with different bandgap energies.Additionally or alternatively, the different materials include a firstmaterial and a second material and the different bandgap energiesinclude a first bandgap energy and a second bandgap energy, the firstmaterial having the first bandgap energy and the second material havingthe second bandgap energy, wherein the first material is capable ofhaving the second bandgap energy with an increase in temperature.Additionally or alternatively, in some examples, at least one of thesubset of epitaxial chips and the second epitaxial chip include the sameone or more materials. Additionally or alternatively, in some examples,at least two of the plurality of epitaxial chips includes the same oneor more materials. Additionally or alternatively, in some examples, theanother epitaxial chip is an adjacent epitaxial chip. Additionally oralternatively, in some examples, the at least one first structure of thefirst epitaxial chip has a gain curve, wherein the at least one secondstructure of the second epitaxial chip has a responsivity curve, andwherein a maximum of the gain curve coincides with a maximum of theresponsivity curve. Additionally or alternatively, in some examples, theat least one first structure and the at least one second structure ofthe same epitaxial chip includes the same one or more materials.Additionally or alternatively, in some examples, the first epitaxialchip further includes at least one second structure, the at least onesecond structure of the first epitaxial chip not configured as adetector that detects light. Additionally or alternatively, in someexamples, one or more of the first epitaxial chip and the secondepitaxial chip exclude other structures. Additionally or alternatively,in some examples, the second epitaxial chip further includes at leastone first structure, the at least one first structure of the secondepitaxial chip not configured as a light source that emits light.

A method of operating a device is disclosed. The method can comprise:during a first time period: emitting a first light from a firstepitaxial chip using a first structure located on the first epitaxialchip, wherein the first epitaxial chip includes the first structure anda second structure, the first structure configured as a light sourcethat emits light, and the second structure configured as a detector thatdetects light; and detecting the emitted first light using a secondstructure located in a second epitaxial chip, wherein the secondepitaxial chip includes a first structure and the second structure, thesecond structure configured as a detector that detects light.Additionally or alternatively, in some examples, the emission of thefirst light from the first epitaxial chip includes biasing the firststructure included in the first epitaxial chip to a first voltage, themethod further comprising: biasing the second structure included in thefirst epitaxial chip to a second voltage, the first voltage differentfrom the second voltage. Additionally or alternatively, in someexamples, the emission of the first light from the first epitaxial chipincludes increasing a temperature of the first structure included in thefirst epitaxial chip until a bandgap energy of the first structure inthe first epitaxial chip is the same as a bandgap energy of the secondstructure in the second epitaxial chip. Additionally or alternatively,in some examples, the method further comprises: during the first timeperiod: emitting a second light from a third epitaxial chip using afirst structure located on the third epitaxial chip, wherein the thirdepitaxial chip includes the first structure and a second structure, thefirst structure configured as a light source that emits light, and thesecond structure configured as a detector that detects light; anddetecting the emitted second light using a second structure located on afourth epitaxial chip, wherein the fourth epitaxial chip includes afirst structure and the second structure, the second structureconfigured as a detector that detects light, wherein emitting the firstlight and emitting the second light occur simultaneously. Additionallyor alternatively, in some examples, the method further comprising:during a second period: emitting a third light using the first structurelocated on the second epitaxial chip; detecting the emitted third lightusing a second structure located on a third epitaxial chip, wherein thethird epitaxial chip includes a second structure located on the thirdepitaxial chip, wherein the third epitaxial chip includes the secondstructure, the second structure configured as a detector that detectslight. Additionally or alternatively, in some examples, the methodfurther comprises: increasing a temperature of the first epitaxial chipuntil a bandgap energy of the first structure in the first epitaxialchip is different from a bandgap energy of the second epitaxial chip,where the first epitaxial chip and the second epitaxial chip include thesame one or more materials. Additionally or alternatively, in someexamples, during the first time period: deactivating the secondstructure included in the first epitaxial chip. Additionally oralternatively, in some examples, the method further comprises: duringthe first time period: deactivating the first structure included in thesecond epitaxial chip.

A device is disclosed. The device can comprise: a plurality of epitaxialchips, wherein each epitaxial chip includes: at least one firststructure, wherein the first structure is configured as a light sourcethat emits light, and at least one second structure, wherein the secondstructure is configured as a detector that detects light, wherein: atleast one of the plurality of epitaxial chips includes a conductivelayer configured as a waveguide for the light source, and a trenchconfigured to electrically isolate the at least one first structure fromthe at least one second structure, wherein the trench is formed deeperthan the conductive layer.

Although the disclosed examples have been fully described with referenceto the accompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Suchchanges and modifications are to be understood as being included withinthe scope of the disclosed examples as defined by the appended claims.

The invention claimed is:
 1. A device comprising: a plurality ofepitaxial chips, wherein at least one of the plurality of epitaxialchips includes: a light source; a detector, a conductive layerconfigured as a waveguide for the light source, and a trench thatelectrically isolates the light source and the detector, wherein thetrench is deeper than the conductive layer.
 2. The device of claim 1,wherein the at least one of the plurality of epitaxial chips furtherincludes: a first heater for controlling a temperature of the lightsource; and a second heater for controlling a temperature of thedetector.
 3. The device of claim 1, wherein: the device furthercomprises a first heater; and operation of the first heater does notaffect the temperature of the detector.
 4. The device of claim 3,wherein: the device further comprises a second heater; and operation ofthe second heater does not affect the temperature of the light source.5. The device of claim 1, wherein: the at least one epitaxial chip is afirst epitaxial chip; the device further comprises a second epitaxialchip; a first heater for controlling the temperature of the firstepitaxial chip; and a second heater for controlling the temperature ofthe second epitaxial chip.
 6. The device of claim 5, wherein the secondheater controls the temperature of the second epitaxial chipindependently of the temperature of the first epitaxial chip.
 7. Thedevice of claim 5, wherein: the second epitaxial chip comprises: asecond light source; a second detector; and a second trench between thesecond light source and the second detector.
 8. The device of claim 1,wherein: a first heater is coupled to the light source of the at leastone epitaxial chip for controlling the temperature of the light source;and the first heater is coupled to the detector of the at least oneepitaxial chip for controlling the temperature of the detector.
 9. Thedevice of claim 1, wherein: the at least one epitaxial chip is a firstepitaxial chip; the device further comprises a second epitaxial chip; afirst heater is coupled to the first epitaxial chip for controlling thetemperature of the first epitaxial chip; and the first heater is coupledto the second epitaxial chip for controlling the temperature of thesecond epitaxial chip.
 10. A device, comprising: a first epitaxial chipcomprising: a first light source for emitting first light; a firstdetector for detecting light; and a first trench separating the firstlight source from the first detector to prevent a first leakage currentfrom forming between the first light source and the first detector; asecond epitaxial chip comprising: a second light source for emittingsecond light; a second detector for detecting the first light; and asecond trench separating the second light source from the seconddetector to prevent a second leakage current from forming between thesecond light source and the second detector.
 11. The device of claim 10,wherein: the device further comprises: a first conductive layerconfigured as a first waveguide for the first light source; and a secondconductive layer configured as a second waveguide for the second lightsource; the first trench is positioned between the first light sourceand the first detector; the second trench is positioned between thesecond light source and the second detector; the first trench is deeperthan the first conductive layer; and the second trench is deeper thanthe second conductive layer.
 12. The device of claim 10, furthercomprising: a first heater coupled to the first epitaxial chip forcontrolling the temperature of the first light source; and a secondheater coupled to the first epitaxial chip for controlling thetemperature of the first detector.
 13. The device of claim 12, wherein:operation of the first heater does not affect the temperature of thefirst detector; and operation of the second heater does not affect thetemperature of the first light source.
 14. A method for operating adevice, comprising: emitting a light from a light source included in anepitaxial chip, detecting the light using a detector included in theepitaxial chip, wherein: the device includes: a trench; and a conductivelayer; the trench that is deeper than the conductive layer; and whereinthe trench electrically isolates the light source from the detector. 15.The method of claim 14, wherein: the conductive layer is configured as awaveguide; and the trench is positioned between the light source and thedetector.
 16. The method of claim 14, further comprising: controlling atemperature of the light source using a first heater; and controlling atemperature of the detector using a second heater.
 17. The method ofclaim 16, wherein: controlling the temperature of the first heater doesnot affect the temperature of the detector; and controlling thetemperature of the second heater does not affect the temperature of thelight source.
 18. The method of claim 14, further comprising:controlling a temperature of the light source using a heater; andcontrolling a temperature of the detector using the heater.
 19. Themethod of claim 14, wherein: the epitaxial chip is a first epitaxialchip; the device further comprises a second epitaxial chip; the methodfurther comprises: controlling the temperature of the first epitaxialchip using a first heater coupled to the first epitaxial chip; andcontrolling the temperature of the second epitaxial chip using a secondheater coupled to the second epitaxial chip.
 20. The method of claim 19,wherein: the light source is a first light source that emits a firstlight; the second epitaxial chip includes a second light source thatemits a second light; and the first light and the second light havedifferent optical properties.